Re: K3 ANT 1-2 isolation
Posted by Mark - G4AXX on Apr 28, 2012; 3:27pm
URL: http://elecraft.85.s1.nabble.com/K3-ANT-1-2-isolation-tp7500652p7509068.html
The isolation between ANT 1 and ANT 2 varies from -76dB at 1.8MHz to -46dB at 50MHz.
This is measured with a signal generator, using the K3 S-meter, with ANT 2, AUX RF and RX ANT IN terminated in 50 Ohms.
The isolation between AUX RF and ANT 1/2 is >95dB (1-30MHz), rising to -70dB (52MHz).
This was measured with an N2PK VNA.
I have tried to dress the unscreened wires from ANT 1 & 2 to the ATU in a way to minimise coupling, but the coupling is dominated by the capacitance of relays K18 & K19.
Using ANT1/2 for Diversity reception means the receivers are never truly independent. There is likely to be more coupling inside the K3 than can usually be achieved by physical separation of the antennas.
Operating Diversity reception with the SUB RX fed from the AUX RF BNC input is the way to go.
73 Mark G4AXX
URL: http://elecraft.85.s1.nabble.com/K3-ANT-1-2-isolation-tp7500652p7509068.html
The isolation between ANT 1 and ANT 2 varies from -76dB at 1.8MHz to -46dB at 50MHz.
This is measured with a signal generator, using the K3 S-meter, with ANT 2, AUX RF and RX ANT IN terminated in 50 Ohms.
The isolation between AUX RF and ANT 1/2 is >95dB (1-30MHz), rising to -70dB (52MHz).
This was measured with an N2PK VNA.
I have tried to dress the unscreened wires from ANT 1 & 2 to the ATU in a way to minimise coupling, but the coupling is dominated by the capacitance of relays K18 & K19.
Using ANT1/2 for Diversity reception means the receivers are never truly independent. There is likely to be more coupling inside the K3 than can usually be achieved by physical separation of the antennas.
Operating Diversity reception with the SUB RX fed from the AUX RF BNC input is the way to go.
73 Mark G4AXX
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